Hydraulic power steering pump having wet type motor with open type magnet

ABSTRACT

Disclosed is a hydraulic power steering pump including a wet type motor with an open type magnet, the hydraulic power steering pump including: a housing; a gear pump module supported at one side of the housing and pressurizing a fluid; and a motor module supported at the other side of the housing and providing driving force to the gear pump module, the motor module including a stator that is supported by the housing and receives electric current based on supplied power, and a rotor that includes a motor rotation shaft rotated by the stator and a permanent magnet generating magnetic force, and an outer side of the permanent magnet being supported by the motor rotation shaft to have an exposed portion exposed toward the stator.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent

Application No. 10-2012-0009019, filed on Jan. 30, 2012 in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein by reference.

BACKGROUND

1. Field

Apparatuses and methods consistent with the exemplary embodiments relateto a hydraulic power steering pump having a wet type motor with an opentype magnet, and more particularly to a hydraulic power steering pumphaving a wet type motor with an open type magnet, in which the wet typemotor is improved in a structure of a rotor.

2. Description of the Related Art

A vehicle is a modern representative transport unit into which a lot ofparts are assembled. In such a vehicle, a steering wheel is typicallyturned so that a driver can control a vehicle's going direction. Thus, awheel connected to the steering wheel is turned and therefore a driversteers the vehicle. Among many parts of the vehicle, a steering deviceallows a driver to steer the vehicle in a direction as s/he desires.

The steering device includes a hydraulic power steering device with apump for supplying hydraulic pressure to assist force given by a driverto turn the steering wheel given by a driver so that the driver caneasily turn the steering wheel.

The hydraulic power steering device (hereinafter, referred to as a‘steering device’) uses a power steering gear to distribute thehydraulic pressure supplied from the hydraulic power steering pumpinstalled in the middle of a steering linkage connected to the steeringwheel, and uses an output shaft to apply the distributed hydraulicpressure to a steerage wheel (a front wheel or a rear wheel), so that adriver can slightly and quickly steer the vehicle with small force. Thatis, the steering device serves to reduce force needed for a driver tocontrol the steering wheel, and prevent a shock from being transferredfrom a road surface to the steering wheel via the front wheel.

The steering device is typically configured with an input transferdevice that generates steering torque and transferring the steeringtorque or changing the direction of the steering torque, a distributiondevice that generates steering assistant force or decreases the steeringassistant force, and an output device that properly converts inputtorque and displacement or changes the direction of the steering torque.Here, the input transfer device includes steering linkage such as asteering wheel, a drag link, a middle shaft, etc., the distributiondevice includes a hydraulic power steering pump, a control valve, etc.,and the output device includes a steering gear having a power cylinderor the like, a tie rod, an end, etc.

Meanwhile, the hydraulic power steering pump is generally classifiedinto two according to driving methods. One is to receive motive powerfrom an engine, and the other is to drive the hydraulic power steeringpump by a separate electric motor without receiving the motive powerfrom the engine. Recently, an electric-driving hydraulic power steeringpump for operating the hydraulic power steering pump has been preferredonly when it is needed to pursue more efficient andenvironmentally-friendly vehicle.

A hydraulic power steering pump system including the electric-drivinghydraulic power steering pump has a little different structure from aconventional engine-driving hydraulic power steering pump. The hydraulicpower steering pump includes an electric motor for providing power, apump assembly for pressurizing a fluid by rotation of an electric motor,a housing for supporting the electric motor and the pump assembly andstoring and guiding the fluid, and a controller for controlling theelectric motor based on an angle of the steering wheel or the like,pressure of the hydraulic power steering pump, etc.

The hydraulic power steering pump sucks oil through a sucking hose asthe engine or electric motor is driven to rotate the pumping gear, anddischarges the pressurized oil. Also, a steering pump is generallycoupled with a flux control valve for controlling the amount of oildischarged. That is, a discharging amount per unit time is increased ordecreased in proportion to a rotation number of the engine since thesteering pump has a constant discharging amount per its rotation.Further, the hydraulic power steering pump is provided with a reliefvalve capable of adjusting the maximum level of fluid pressure not to behigher than necessary.

Recently, more and more hydraulic power steering pumps driven by theelectric motor have been developed in light of fuel efficiencyimprovement and environmentally-friendly trend. Further, a wet typemotor through which operating fluid passes is more preferable inconsideration of cooling or the like.

As a related art, there is an example of Korean Patent Publication No.2006-5340 (2006 Jan. 17).

A driving motor 12 of the related art shown in FIG. 1 includes a rotor36, a shaft 38 coupled to the rotor 36, and a stator 40 arranged aroundthe rotor 36. Here, the rotor 36 has a structure that a metal coverfully surrounds an internal permanent magnet, thereby causing problemsof deteriorating magnetic properties of the permanent magnet, increasingcosts of manufacturing molding or the like, and lowering economicalefficiency due to manufacture, assembly, etc.

SUMMARY

One or more exemplary embodiments may provide an aspect of the presentinvention is to provide a hydraulic power steering pump having a wettype motor with an open type magnet, in which a coupling structure of apermanent magnet arranged in the rotor is improved to enhance magneticproperties of the permanent magnet and thus enhance the efficiency ofthe motor.

Another exemplary embodiment provides a hydraulic power steering pumphaving a wet type motor with an open type magnet, in which a couplingstructure of a permanent magnet is simplified to reduce costs of moldingor the like and thus improve economical efficiency.

Still another exemplary embodiment provides a hydraulic power steeringpump having a wet type motor with an open type magnet, which has asimple structure to simplify processes for manufacture, assembly, etc.

According to an aspect of another exemplary embodiment, a hydraulicpower steering pump including a wet type motor with an open type magnetis provided including: a housing; a gear pump module supported at oneside of the housing and pressurizing a fluid; and a motor modulesupported at the other side of the housing and providing driving forceto the gear pump module, the motor module including a stator that issupported by the housing and receives electric current based on suppliedpower, and a rotor that includes a motor rotation shaft rotated by thestator and a permanent magnet generating magnetic force, and an outerside of the permanent magnet being supported by the motor rotation shaftto have an exposed portion exposed toward the stator.

The rotor may be arranged within flow of a fluid.

The rotor may include a yoke holder coupled to the motor rotation shaft,a yoke supported by the yoke holder, and the permanent magnets plurallyarranged outside the yoke, and the yoke holder includes a permanentmagnet holder to support one end of each permanent magnet along alengthwise direction of the motor rotation shaft.

The yoke holder may include ribs that divide the yoke holder in acircumferential direction to separate the permanent magnets from eachother if the permanent magnets are arranged in the circumferentialdirection of the yoke holder.

The hydraulic power steering pump may further include a separationpreventing cab member including a skirt surrounding the other end of thepermanent magnet along the lengthwise direction of the motor rotationshaft so that each permanent magnet coupled to the yoke can be preventedfrom separation in the circumferential direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of exemplary embodiments,taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a hydraulic power steeringpump having a motor according to an exemplary embodiment,

FIG. 2 is a partially cut-open perspective view of FIG. 1,

FIG. 3 is an exploded perspective view of a rotor in FIG. 1, and

FIG. 4 is a cross-section view of FIG. 3.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of a hydraulic power steering pumphaving a wet type motor with an open type magnet will be described withreference to FIGS. 1 to 4.

FIG. 1 is an exploded perspective view of a hydraulic power steeringpump having a motor according to an exemplary embodiment, FIG. 2 is apartially cut-open perspective view of FIG. 1, FIG. 3 is an explodedperspective view of a rotor in FIG. 1, and FIG. 4 is a cross-sectionview of FIG. 3.

According to an exemplary embodiment, a hydraulic power steering pump100, which generates hydraulic pressure for assisting torque of a steerwheel for a vehicle, is a gear type pump among various types of pump. Asshown in FIGS. 1 and 2, the hydraulic power steering pump 100 includes ahousing 110 accommodating a working fluid and having a partition wallmember 117 for partitioning a space, a cap 190 coupled to one side ofthe housing 110 and sealing up the housing 110, a housing cover 180coupled to and sealing up the other side of the housing 110, a gear pumpmodule 130 accommodated between the housing 110 and the cap 190 andpressurizing the working fluid as being coupled to the partition wallmember 117, a sucking fluid shock absorber 195 a, 195 b storing theworking fluid sucked by the gear pump module 130 and decreasingpulsation of the sucked fluid, and a pressurized shock absorber 132provided in the gear pump module 130 and decreasing the pulsation of thepressurized fluid discharged from the gear pump module 130.

For reference, upward and downward directions in FIGS. 1 and 2 will berespectively defined as up and down directions, as necessary.

The housing 110 forms most of an outer appearance of the hydraulic powersteering pump 100, and is hard enough to support and accommodate variouselements. The housing 110 may be made of steel materials, or may be castwith aluminum alloy to be lightweight.

The housing 110 includes the partition wall member 117 for partitioningan inner space thereof into upper and lower spaces. A gear pump moduleaccommodating unit 113 is formed above the partition wall member 117 andaccommodates the gear pump module 130, and a motor module accommodatingunit 115 is formed below the partition wall member 117 and accommodatesthe motor module 150.

Also, the partition wall member 117 is formed with a discharging hole119 at one side thereof, through which the pressurized working fluid forgiving assisting force to the steering wheel is discharged from thehydraulic power steering pump 100. Alternatively, the discharging hole119 may be formed at a necessary position of the housing 110.

Further, the partition wall member 117 is formed with a shaft hole 117 apenetrating the center thereof so that torque of the motor module 150can be transmitted to the gear pump module 130, a central suckingchannel 117 c formed so that the working fluid can flow from the secondsucking fluid shock absorber 195 b to the gear pump module 130, and avertical sucking channel 117 b formed to guide the fluid introduced fromthe sucking hole 193 to flow from the first sucking fluid shock absorber195 a to the second sucking fluid shock absorber 195 b.

The motor module 150 includes a wet type motor accommodated in a secondsucking fluid shock absorber 195 b and being in contact with the workingfluid.

Further, the hydraulic power steering pump 100 may include a drivingcircuit module 170 that applies electric power to the motor module 150,controls the motor module 150 to be driven, transmits and receivesvarious signals to and from an engine control means (not shown), andtransmits and receives signals from and to a sensor. The driving circuitmodule 170 includes a driving circuit member 175 having a printedcircuit board (PCB) or the like for communication and control of varioussignals, and a driving circuit module supporting member 173 supportingthe driving circuit member 175 and coupled to the housing 110 so thatthe driving circuit member 175 can be isolated from the working fluid.

Further, the reference numeral of ‘177’ indicates a wiring entrance viawhich an electric wire, a cable, etc. connected to the driving circuitmodule 170 or the motor module 150 can enter or exit.

The gear pump module 130 includes the gear pump housing 110, a gear pumpcover 133 sealing up the gear pump housing 110, and a pumping unit 135provided in the gear pump housing 110 and pressurizing the suckedworking fluid toward the engaged pumping gear 135 a. The gear pumpmodule 130 includes a pump module holding member 139 a having a bolt forcoupling the gear pump module 130 with the partition wall member 117,and a relief valve 138 discharging a high pressurized working fluidpressurized by the pumping unit 135 toward a low pressure portion ifdischarging pressurized working fluid pressure reaches some degree.Here, the high pressure working fluid of the pressurized shock absorber132, discharged from the relief valve 138, may be discharged to a firstsucking fluid shock absorber 195 a where a low pressure working fluid isstored.

The gear pump housing 110 includes the pumping unit 135 accommodated ina pumping-unit accommodating portion 136 to pressure a low-pressureworking fluid up to a high-pressure working fluid.

The pumping unit 135 includes the pumping gears 135 a engaged to eachother to pressurize the low-pressure working fluid into thehigh-pressure working fluid, the gear housing 110 supporting the pair ofpumping gears 135 a at opposite ends, and a relatively long gear pumprotation shaft 137 and a relatively short gear pump rotation short shaft137 b which are coupled to a motor rotation shaft 151 and allow thepumping gears 135 a to turn.

The pressurized shock absorber 132 is a space formed in a verticallylengthwise direction along a partial circumferential direction of thegear pump internal housing 131 d. The cross-section of the pressurizedshock absorber 132 is narrowing along a flowing direction of the workingfluid from a discharging area of the pumping unit 135 to the dischargingdirection of the gear pump module 130.

Although it is not shown, the pressurized shock absorber 132 may forexample have a ‘U’-shaped cross-section in the discharging area of thepumping unit 135, and be approximate to a circle as the ‘U’-shapedcross-section is tapering along the flowing direction of the workingfluid discharged from the gear pump module 130.

Thus, the cross-section becomes wider in such a narrow channel, i.e., ashock absorber sucking hole (not shown), and becomes narrower again indirection toward a narrow channel, i.e., a shock absorber discharginghole (not shown), thereby forming the pressurized shock absorber 132 sothat the pulsation of the pressurized and discharged working fluid canbe effectively reduced via the pressurized shock absorber 132.

The sucking fluid shock absorber 195 a, 195 b includes a first suckingfluid shock absorber 195 a provided as a space among the partition wallmember 117, the cap 190 and the gear pump module 130, and a secondsucking fluid shock absorber 195 b provided as a space among thepartition wall member 117, the housing cover 180 and the motor module150. That is, the maximum space as possible may be formed so that thepulsation generated in the working fluid as the working fluid sucked andpressurized by the pumping gear 135 a flows can be absorbed in theworking fluid itself.

The cap 190 is coupled to a top of the housing 110 so as to prevent theworking fluid filled in the first sucking fluid shock absorber 195 afrom leaking. The cap 190 is formed with the sucking hole 193 at oneside thereof to guide the working fluid introduced from a tank (notshown) storing the working fluid to the hydraulic power steering pump100. Alternatively, the sucking hole 193 may be formed in the housing110 as necessary. The cap 190 may be molded with a material such as aplastic compound to reduce weight.

With this configuration, an effect on reducing the pulsation due to thechannel of the hydraulic power steering pump 100 according to anexemplary embodiment will be schematically described.

First, the hydraulic power steering pump 100 of a gear type repetitivelyincreases and decreases the discharging amount due to characteristics ofthe pumping gear 135 a, and the increase/decrease of the dischargingamount causes the pulsation of the hydraulic power steering pump 100.Meanwhile, the pulsation of the discharging side causes the pulsation ofthe sucking side. To prevent the pulsation of the sucking or dischargingside, a large space is provided in the channel for sucking ordischarging the working fluid so that the working fluid stored in thelarge space can reduce the pulsation. Further, the channels narrowerthan such a large space are formed in front and back of the storagespace and thus prevent the pulsation from being transferred to anotherchannel.

That is, the working fluid in the narrow sucking hole 193 is guidedtoward a large storage space, i.e., toward the first sucking fluid shockabsorber 195 a while being sucked in the pumping unit 135, and guided bya plurality of narrow vertical sucking channels 117 b formed in thepartition wall member 117 toward a large space, i.e., toward the secondsucking fluid shock absorber 195 b.

Further, the fluid stored in the second sucking fluid shock absorber 195b is pressurized in the pumping unit 135 via the central sucking channel117 c penetrating the center region of the partition wall member 117,guided to the relatively large space, i.e., to the pressurized shockabsorber 132 via a relatively narrow shock absorber sucking hole (notshown), and guided to the discharging hole 119 of the hydraulic powersteering pump 100 via the narrow discharging hole 119, the cross-sectionof which gets narrower, thereby acting as the pressurized working fluid.That is, the volume of the channel for the working fluid is enlarged sothat the expanded working fluid can prevent the pulsation at thedischarging to sucking sides.

Thus, the pulsation of the working fluid sucked into or discharged fromthe pumping unit 135 can be effectively reduced through the suckingfluid shock absorber 195 a, 195 b and the pressurized shock absorber132. Also, the sucking fluid shock absorber 195 a, 195 b may fully use aspace formed by the pump housing, the cap 190 and the housing cover 180,and the pressurized shock absorber 132 is formed in the pump housing 110so that the hydraulic power steering pump 100 can be formed morecompactly.

The motor module 150 is coupled to and supported by the motor moduleaccommodating unit 115 of the housing 110. The motor module 150 includesa stator 153 provided to receive electric current based on externalelectric power and supported by the housing 110, and a rotor 155provided rotatably corresponding to the stator 153, coupled to thepartition wall member 117 in the middle region of the housing 110, andhaving the permanent magnet 161 and the motor rotation shaft 151. Thepermanent magnet 161 includes an exposed portion 161 a at the outsidethereof exposed toward the stator 153.

The stator 153 is the same as a general motor module 150, and thusdetailed descriptions thereof will be avoided as necessary.

The rotor 155 includes a yoke holder 157 coupled to the motor rotationshaft 151, a yoke 159 having a first side coupled to the yoke holder 157and a second side coupled to a separation preventing cab member 163, andthe permanent magnet 161.

The yoke holder 157 is coupled to the motor rotation shaft 151, and onan upper side thereof includes a yoke coupling portion 157 c recessed tocouple with the yoke 159 and a permanent magnet holder 157 a to beengaged with the permanent magnet 161, respectively. The yoke couplingportion 157 c and the permanent magnet holder 157 a may have variousshapes corresponding to the shapes of the yoke 159 and the permanentmagnet 161. Further, as necessary, adhesive or the like may be used tobe coupled to the yoke coupling portion 157 c and the permanent magnetholder 157 a.

Meanwhile, the yoke holder 157 may be provided with ribs 157 b formedbetween the permanent magnets 161 so that the plurality of permanentmagnets 161 coupled in a circumferential direction can be separated anddivided in the circumferential direction. As necessary, the ribs 157 bmay form an inclination portion inclined to the motor rotation shaft 151so that the fluid can flow through a gap between the rotor 155 and thestator 153 as the rotor 155 rotates. Thus, the flow of the fluid iscaused between the stator 153 and the rotor 155 to thereby effectivelydissipating heat generated in the motor module 150.

Further, the separation preventing cab member 163 is provided to holdthe upper sides of the yoke 159 and the permanent magnet 161 after theyoke 159 and the permanent magnet 161 are coupled to the yoke holder157. In this case, the separation preventing cab member 163 includes askirt 163 a bent down from a top plate thereof so as to surround theupper end of the permanent magnet 161 or as necessary the upper end ofthe yoke 159. Thus, an inside of the permanent magnet 161 may be coupledto the yoke 159 by adhesive or the like, an outer lower end of thepermanent magnet 161 may be supported by the permanent magnet holder 157a (refer to ‘K3’ in FIGS. 3 and 4), an outer upper end of the permanentmagnet 161 may be supported by the skirt 163 a (refer to ‘K1’ in FIGS. 3and 4), an outer middle region of the permanent magnet 161 may form anexposed portion 161 a exposed toward the rotor 155 (refer to ‘K2’ inFIGS. 3 and 4).

A process of manufacturing the motor module 150 with this configurationaccording to an exemplary embodiment will be described with reference toFIGS. 3 and 4.

First, the yoke holder 157 is coupled to the motor rotation shaft 151.As described above, the yoke holder 157 is formed with the permanentmagnet holder 157 a, the rib 157 b and the yoke coupling portion 157 c.

Next, the yoke 159 is coupled onto the upper side of the yoke couplingportion 157 c recessed in the yoke holder 157.

After coupling the yoke 159, adhesive or the like is applied to theregion for coupling with the yoke 159 and then the plurality ofpermanent magnets 161 is coupled to the permanent magnet holder 157 a.The plurality of permanent magnets 161 may be arranged to be spacedapart from each other by the ribs 157 b in the circumferentialdirection.

Next, the separation preventing cab member 163 is coupled to the uppersides of the permanent magnet 161 and the yoke 159 so that the permanentmagnet 161 can be firmly supported in the yoke holder 157 by the end ofthe permanent magnet 161 surrounded with the skirt 163 a without beingseparated in the circumferential direction or in an upward direction.

Thus, both ends of the permanent magnet 161 are not separated in aradial direction or in a lengthwise direction by the permanent magnetholder 157 a and the skirt 163 a, respectively, and at the same time themiddle region of the permanent magnet may form the exposed portion 161 aexposed in the circumferential direction.

Here, data comparison between the related art and the present embodimentis as follows.

The following [Table 1] shows experimental data under the condition thatthe permanent magnet of the rotor is fully surrounded according to therelated art and experimental data under the condition that the permanentmagnet of the rotor is exposed according to an exemplary embodiment.

TABLE 1 Volt- Effi- Torque Speed Output Input Current age ciency N-m rpmkW W A V % Related 0.600 2235 0.140 220.5 17.60 12.31 63.7 art 1.2001098 0.138 384.4 34.54 11.13 35.9 Present 0.600 3193 0.202 270.14 20.1613.40 74.7 embodi- 1.200 2816 0.352 462.21 34.91 13.24 76.2 ment Note

As shown in [Table 1], under the same condition that a constant torqueof 0.600 N-m is generated, the related art shows the efficiency of 63.7%but the present embodiment shows 74.2%, which shows that the efficiencyof the present embodiment is increased by about 16%. Likewise, under thesame condition that a torque is 1.2 N-m, the related art shows theefficiency of 35.9% but the present embodiment shows 74.7%, which showsthat the efficiency of the present embodiment is significantly increasedas compared with that of the related art.

Thus, on the contrary to the related art, the permanent magnet 161provides the maximum exposed portion 161 a as possible, and thusmagnetic force generated by the permanent magnet 161 or the like is notinterfered to thereby enhance magnetic properties and improve theefficiency of the motor. Also, the permanent magnet is not fullysurrounded, so that the structure for supporting the permanent magnetcan become simpler and more convenient, thereby lowering molding costsor the like. In addition, the simple structure may cause the number ofparts to be reduced, thereby simplifying manufacture, assembly, etc. andraising economical efficiency.

According to an exemplary embodiment, there is provided a hydraulicpower steering pump having a wet type motor with an open type magnet, inwhich a coupling structure of a permanent magnet arranged in a rotor isimproved to enhance magnetic properties of the permanent magnet tothereby increase efficiency of a motor, a structure of coupling thepermanent magnet is simplified to lower costs of manufacturing moldingor the like and thus raise economical efficiency, and the simplestructure causes processes of to be simplified.

Although a few exemplary embodiments have been shown and described, itwill be appreciated by those skilled in the art that changes may be madein these exemplary embodiments without departing from the principles andspirit of the invention, the scope of which is defined in the appendedclaims and their equivalents.

What is claimed is:
 1. A hydraulic power steering pump comprising a wettype motor with an open type magnet, the hydraulic power steering pumpcomprising: a housing; a gear pump module supported at one side of thehousing and pressurizing a fluid; and a motor module supported at theother side of the housing and providing driving force to the gear pumpmodule, the motor module comprising a stator that is supported by thehousing and receives electric current based on supplied power, and arotor that comprises a motor rotation shaft rotated by the stator and apermanent magnet generating magnetic force, and an outer side of thepermanent magnet being supported by the motor rotation shaft to have anexposed portion exposed toward the stator.
 2. The hydraulic powersteering pump according to claim 1, wherein the rotor is arranged withinflow of a fluid.
 3. The hydraulic power steering pump according to claim1, wherein the rotor comprises a yoke holder coupled to the motorrotation shaft, a yoke supported by the yoke holder, and the permanentmagnets plurally arranged outside the yoke, and the yoke holdercomprises a permanent magnet holder to support one end of each permanentmagnet along a lengthwise direction of the motor rotation shaft.
 4. Thehydraulic power steering pump according to claim 3, wherein the yokeholder comprises ribs that divide the yoke holder in a circumferentialdirection to separate the permanent magnets from each other if thepermanent magnets are arranged in the circumferential direction of theyoke holder.
 5. The hydraulic power steering pump according to claim 3,further comprising a separation preventing cab member comprising a skirtsurrounding the other end of the permanent magnet along the lengthwisedirection of the motor rotation shaft so that each permanent magnetcoupled to the yoke can be prevented from separation in thecircumferential direction.